Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

661
FXUS63 KLOT 100718
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
218 AM CDT Tue Mar 10 2026

.KEY MESSAGES...

- Areas of dense fog this morning, mainly near/north of I-80.

- Severe thunderstorms this afternoon and evening, with the
  potential for very large hail, damaging winds and tornadoes.

- Potential for heavy rain and localized flash flooding this
  afternoon into Wednesday morning.

- Small potential for damaging winds continuing into Wednesday
  morning across our far south and east.

- Possible very strong winds (45+ mph) Thursday night/Friday.

&&

.DISCUSSION...
Issued at 218 AM CDT Tue Mar 10 2026

Through Wednesday:

Moisture is surging northward early this morning, with
dewpoints pushing into the upper 50s and lower 60s across the
region. Pockets of low stratus and shallow mist have recently
developed, and this will likely continue to expand north of I-80
and the Illinois river through daybreak. Surface flow is
forecast to remain elevated, but given the recent expansion of
sub 1/2 mile visibilities, may need to shortly consider a dense
fog advisory for parts of the area.

Somewhat of a complex severe weather setup is evident later
this afternoon and overnight with quite a few moving parts and
generally nebulous/subtle large scale forcing mechanisms. As a
result, uncertainty in the precise evolution of thunderstorms
remains, but the ceiling on the severe weather potential in the
region is anomalously high for this time of year.

The first key player is an extremely shallow cold front that`s
presently rolling down the lake and into southern Wisconsin.
This front is so shallow that it`s not super evident even on the
MKX radar, which certainly corroborates forecast soundings from
the NAM/NAMNest which depict the frontal inversion sitting
around 700 feet. These types of shallow early-spring boundaries,
enhanced by the cold Lake Michigan waters, often have an
impressive ability to plow southward and undercut even deep
moist boundary layers. This backdoor front will likely be no
exception, with the latest guidance suggesting this will surge
south to near a Rockford - St. Charles - Crown Point, IN line by
midday before settling in the vicinity of to just south of the
I-80 corridor by mid afternoon before becoming quasistationary.
Behind the front, temperatures will fall to either side of 40 at
the lake front and into the 40s/maybe low 50s inland as low
stratus expands atop the frontal inversion (perhaps with some
scattering in the afternoon, mainly along the southern flanks).

While low stratus may develop south of I-80 through this
morning, forecast soundings indicate this would be quite thin
and likely to mix out readily. As a result, temperatures are
expected to surge through the 70s, if not tagging 80 on a
localized basis towards central Illinois this afternoon. As
dewpoints surge into the mid and upper 60s, an expansive
elevated mixed layer characterized by 500-700 mb lapse rates of
7.5 to 8.5 C/km will overspread the region leading to a rapid
increase in conditional instability with MLCAPE values progged
to rise through 2000-3000 J/kg during the afternoon.

Given the relatively warm base to the EML, things look to remain
decidedly capped to surface-based convection through at least
early afternoon in the region until additional modest ascent
approaches the region. Key player number 2 appears to be a
mid-level perturbation that`s currently pushing out of the
Texas/Oklahoma Panhandles and into Kansas. While global
guidance has been fairly steady with this feature, have noted
some more significant variability with the CAMs which in turn
seems to be playing a role in the run-to-run variability in
convective initiation (or not) by early-mid afternoon near and
southeast of the Quad Cities as the associated DCVA with this
feature is not particularly robust, and the main jet core may
only provide a glancing blow across the sharpening
quasistationary/warm frontal zone before continuing
northeastward. Whether explosive CI occurs in the vicinity of a
Moline to Ottawa line in the roughly 2 - 4 PM timeframe remains
a key detail to iron out. If CI occurs here, this would be very
concerning as semi-discrete supercellular convection would be
favored within a strongly sheared environment supportive of all
severe hazards including tornadoes, very large hail, and
damaging winds.

While recent runs of the HRRR have mostly lost this convection, the
fact that the globals (GFS, ECMWF, UKMET) have been fairly
steadfast in convective development in this zone remains
concerning. Have continued to paint generally chance PoPs in
this corridor during the afternoon, and we`ll need to carefully
monitor this zone. *IF* semi-discrete cells can develop and
sustain in this corridor south of the front, there would
certainly be a threat for strong tornadoes.

Isentropic upglide atop the sharp frontal inversion and
generally increasing large scale forcing as the main surface low
approaches will eventually lead to an expansion of thunderstorms
through Tuesday evening. Surface based convection south of the
front will continue to pose an all-hazards severe threat deep
into the evening. While a tornado threat can occasionally occur
many miles north of warm fronts, this appears unlikely in this
scenario given the sharp nature of this feature. As a result,
any storms that track northeast and atop the frontal zone will
quickly become elevated. Additional convection will likely
develop through the evening across northern Illinois in response
to intensifying upglide. Storms north of I-80 will pose a threat
for large--possibly very large--hail as forecast soundings
reveal strong inflow-layer storm-relative winds and significant
1-7 km shear. If very robust supercells can sustain themselves,
isolated damaging wind gusts may still materialize north of the
front as well.

Regarding the flood potential: the generally southwesterly
500-mb flow does not exactly match some of the more significant
Maddox type flash flood setups in the region. That said,
corridors of southwest to northeast oriented thunderstorms will
pose a threat for at least localized training and very heavy
rainfall. Some increased concern for flooding exists for areas
like Chicago and parts of the south and southeast burbs where
heavy rain fell a few days ago. Will refresh the Hydrologic
Outlook. Can`t rule out needing a targeted flash flood watch
down the line if corridors of heavier training convection can be
nailed down a bit better.

The threat for strong-severe storms will possibly continue
through the night. Noting another early window Wednesday
morning as a possibly convectively-augmented MCV and vort lobe
tracks across our southeast around or just after daybreak.
Guidance suggests that surface-based convection would still be
possible during this period south and east of a Pontiac to
Rensselaer line, with a threat for damaging wind gusts and
perhaps some embedded QLCS tornado threat. This is somewhat
lower confidence at this time, but something we`ll need to keep
an eye on.

Fairly widespread showers will then occur through the balance of
Wednesday as a cold front eventually works its way through the
area. Some potential for precip to turn over to a little snow
across far northern Illinois, but temperatures look to remain
largely at or above freezing. Could even be a potential for a
little drizzle as things come to an end, but again not concerned
about wintry impacts at this point due to forecasted
temperatures. Have boosted wind gusts Wednesday afternoon as
steepening boundary layer lapse rates should result in at least
periodic 30-40 mph gusts.

Carlaw


Wednesday night through Monday:

It looks like we`ll get a bit of a break Wednesday night into
Thursday as high pressure shifts off to our south. Noting some
potential for fairly deep mixing Thursday afternoon and for RH
values to fall around or under 30 percent with breezy westerly
winds. Given the rain forecast over the next 24 hours, this
doesn`t currently look like an elevated fire threat.

Thursday night into Friday, a robust surface low (mid 980s mb)
is forecast to track to our north, roughly across the Door
Peninsula and across northern lower Michigan. Noting a huge low-
level mass response in the guidance, with 850 mb winds near 70
knots advertised across the guidance suite. While some low cloud
cover and at least spotty light precipitation (rain) will be
possible, deeper-than-typical mixing during the late overnight
hours into Friday morning may yield a significant increase in
winds and gusts. Concerningly, latest GFS soundings show roughly
50 knot boundary layer mean winds during this time frame, with
even steeper lapse rates developing after daybreak Friday in the
cold advection regime. Have increased winds and gusts a bit
with this forecast package above the NBM-delivered values, but
suspect things remain notably underdone at this time. At this
time, can`t rule out high wind warning type winds and gusts into
Friday morning given the latest model trends.

Winds will ease sharply Friday evening as high pressure again
builds across the region. There may be some additional precip
chances towards the Saturday night - Sunday morning timeframe
as mid-level frontogenesis intensifies in advance of the next
disturbance, although the latest guidance suggests most of this
activity may end up shifting largely north of the region.
Thereafter, global deterministic and ensemble guidance suggest
the potential for yet another robust surface low spinning up in
the general vicinity on Sunday and into Sunday night. A much
colder airmass bottled up to the north looks like it`ll get
dislodged with this feature and surge across our area during
this timeframe. While model variability remains somewhat high at
this juncture, can`t totally rule out old man winter making
another return to the region with some snow potential into early
Monday morning.

Carlaw

&&

.AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 1232 AM CDT Tue Mar 10 2026

Primary forecast concerns include...

Wind shift to northeast after daybreak this morning.
Low mvfr/ifr cigs through the period.
Chance of thunderstorms this afternoon/evening.
Potential for fog and ifr/lifr vis at times.

Southerly winds will turn more southwesterly overnight and then
shift north/northeast with a cold front after daybreak. Winds
will turn more northeasterly then easterly later today with
speeds in the 10-12kt range and some higher gusts at times.

A low mvfr cig continues to develop and expand across northeast
IL early this morning as low level moisture continues to
increase from the south. While confidence is low, what guidance
does show this, shows it continuing through daybreak though
there will likely be breaks and perhaps a southern edge that may
work its way north through the terminals. For now, opted to
carry a 1kft cig through daybreak. Cigs are likely to lower into
ifr and possibly lifr later this morning behind a cold front
with only medium confidence for this time period. Low confidence
for cigs lifting back to low mvfr this afternoon.

There is also patchy fog developing across parts of north
central IL, as well as over Lake Michigan. Fog is likely to
expand in coverage early this morning and then when winds turn
northeast off the lake, additional fog may move inland. For now
have held with mvfr vis but this may end up too high and lower
visibilities may be needed with later updates.

Scattered thunderstorms are expected to develop by late this
afternoon. While there is reasonable consensus these first
storms will be just south of the terminals, they will be close
enough to warrant prob thunder mention for ORD/MDW/DPA, tempo at
GYY. Additional thunderstorms are expected this evening and
current tempo mention seems reasonable during this time period.
Any thunderstorms that form may become severe with large hail
the main threat for thunderstorms at the terminals, except at
GYY where all severe threats will be possible. Heavy rain will
also be possible with these thunderstorms.

Outside of the thunderstorms this evening, there may be lifr and
even vlifr cigs along with fog. Confidence is low for how low
visibilities may drop with fog and changes can be expected with
later forecasts.

Most of the thunderstorm activity is expected to be moving east
and southeast of the terminals after 06z with lingering showers
or drizzle and winds turning northerly then north/northwest. cms

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

Visit us at weather.gov/chicago